Copper removal from aqueous systems:: Biosorption by Pseudomonas syringae

The potential of two strains of Pseudomonas syringae (Blue and Brown) to remove copper from aqueous solutions has been investigated and assessed against the synthetic Linde LZ-52Y aluminosilicate zeolite. The two bacterial strains were tolerant to copper and were able to grow in media doped with concentrations of up to 1000 ppm. The biosorptive capacity and the mechanism of copper uptake were investigated using "active" and "inactive" species grown in nutrient-rich and complex media. The degree of copper removal by ion exchange with the Y zeolite is reported and compared with that achieved when using the biosorbents under the same treatment conditions. The bacteria were harvested, freeze-dried, and used to adsorb copper under starved and glucose activated conditions. The need to distinguish between "bio-uptake" and the action of complexing agents that may be present are highlighted. The experimental data are fitted to standard Freundlich, BET, and Langmuir adsorption models where the latter yielded both meaningful theoretical maximum adsorption capacities and adsorption affinity coefficients. These values are discussed in terms of the sorbate/sorbent interactions, which are shown to involve a passive mechanism where the majority of the copper attaches to the outer cell wall.